Yes. Practice always before you use something. Try only what is value added from using technology, that is, if a drawing, a transparency or a Textbook photo is better by all means use it instead.

Everyone has some disasters. Students tend to be tolerant. Always have a Backup plan if the technology fails. Always allow extra time, especially on Exams using technology.

No, I have not had failures, yet. Don't forget to keystroke your instructions before you give them to the students.

Oh yeah! Wolfram once turned off the key served Mathematica® right in the middle of the quarter when labs were due. We don't use Mathematica® anymore. Maple® doesn't like being key served to an Apple® based system and runs slowly and crashes all the time. If more than eight computers try to talk to the same web site (e.g., Devaney's above) simultaneously in a lab based situation, the whole thing slows to a crawl. Hardware breaks regularly, preferably when you are trying to do a demo in front of 150 students. Disaster awaits around every corner, with every update of software. ALWAYS have an alternative at hand in case the system goes down in the middle of class.